פרשת ויקהל- setting limits

The question is why would one think that he can do malacha outside the Beis Hamikdash?

Although many Halachos are black and white, muttar is assur, there are some exceptions to these rules, rarely do we even bend the rules.

as we see above even when something is seemingly allowed for a cause we have to understand why it is allowed and view it as an exception. Part of a military slope is seeing it as an allowance in one case and applying this exception to other examples where it doesn't apply to and eventually it becomes muttar.

The Yalkut is saying that the Torah is very clear that this is an exception and only here can we use it.

^{https://www.chabad.org/therebbe/article_cdo/aid/2781550/jewish/The-Rebbe-and-the-Reform-Leader.htm}

On another occasion, I was discussing with the Rebbe the differences between Chabad and the Reform or Conservative movements. The Rebbe remarked that when you ask a question in Jewish law of a Reform or Conservative rabbi, his answer will take into account every possibility—he will tell you that you can go this way, you can go that way, you can do this much, you can do more, you can do less, and in the end, you will be invited to make your own choice, and you will be told not to feel guilty about making such a choice.

As the Rebbe said to me, “The great fault of Conservative and Reform is not that they compromise, but that they sanctify the compromise, still the conscience, and leave no possibility for return.”

Whereas, when you ask such a question of a Chabad rabbi, his answer will take into account your potential. He may also present you with options. If you cannot fulfil every mitzvah at this time, he may give you the option of doing what you can do now, and gradually trying to do more—to eventually fulfil what is asked of you by G‑d.